Field of the Invention and Related Art Statement
This invention relates to an optical card and an apparatus for writing and/or reading data onto and/or from an optical card.
An optical card has been disclosed in PCT Publication WO 82/020968, and Japanese Publication Kokai Nos. 61-51,287 and 61-150,391.
In general, the optical card comprises a substrate in the form of a rectangular sheet made of synthetic resin, a data record layer applied on the substrate and a protection layer applied on the data record layer and made of transparent synthetic resin. The reading and/or writing of data for such an optical card is effected by projecting a laser beam onto the data record layer via the transparent protection layer. There have been proposed various kinds of optical cards having different constructions. In almost all optical cards, the data record layer includes a number of tracks extending in parallel with each other usually in the longitudinal direction of the card. Each track is composed of a data record area, and an address data area in which address data for identifying the relevant track is recorded.
In general, the track construction of the optical cards are different from each other in accordance with applications thereof. For instance, the number of bytes in a sector is different for optical cards of different applications. In an application in which a large amount of data has to be read out and/or written in each operation, the number of bytes in a sector must be large, such as 1024 bytes or 2048 bytes. On the contrary, in an application in which a small amount of data is handled in each operation step, the number of bytes per sector is set to a small value such as 32 bytes or 16 bytes. In this manner, the numbers of bytes in a sector of optical cards for various applications differ from each other. This results in that the numbers of sectors in a track are also different for various kinds of optical cards. The optical cards having different track constructions could not be treated by the same reading and/or writing apparatus. That is to say, each apparatus is designed and manufactured to be exclusively used for optical cards having predetermined track constructions. This causes a demerit upon makers for manufacturing writing and/or reading apparatuses. In order to use the reading and/or writing apparatus for various kinds of optical cards, there have been proposed various methods. In one method, the writing and/or reading apparatus is readjusted by a user in accordance with particular track constructions of optical cards to be used. In another method, the writing and/or reading apparatus comprises a plurality of circuit sections each being constructed to meet with respective track constructions and a switching circuit for selecting one of said circuit sections in accordance with the track construction of optical cards to be used. The switching circuit may be manually operated by a user or is automatically operated with the aid of commands transmitted from a host computer. However, in these known methods, the user must recognize the track construction of respective optical cards which the users want to use. This requires the cumbersome and time consuming operation of the user. Moreover, in the known optical card system, it is impossible to utilize a writing and/or reading apparatus for plural kinds of optical cards having different track constructions. In other words, once the writing and/or reading apparatus has been adjusted to use a predetermined kind of optical card, the apparatus could no more treat any optical cards having different track constructions. This would restrict the versatility of the optical cards.
Further, in a known optical card, all the tracks in the card have the same track construction. Usually, each of tracks in a card constitutes a single sector which includes 1024 bytes. This is due to the fact that the track construction has to be determined in such a manner that the longest data can be recorded in one sector. It thus is apparent that the data record area of the optical card could not be utilized efficiently in case of writing data having a shorter length.